Should I install a caching system?

I've been wondering about using a caching system (i.e. one of the systems listed in AdminCP->Advanced Configuration->Data Storage - APC, Memcached, Redis etc).  My site is pretty small, but I keep reading that using a cache system nevertheless improves performance across the board because the data retrieval is faster on any level.  But before I install one of the systems on my VPS I was wondering if about opinions here re: whether it's really necessary/worthwhile for small sites and, if so, which one I should use?

Thanks in advance!